title: Solution electrostatics beyond pH: a coarse grained approach to ion specific interactions between macromolecules.
abstract: Oblivious to ion specificity, pH has been a key parameter for macromolecular solutions for little more than a century. We here widen the concept by describing the ionization of macromolecules not only via pH, but also pX where X are other binding species. Using binding constants, measured by NMR, of chloride and thiocyanate to amino acid motifs on y-crystallin, we calculate i) titration curves as a function of pH and pX and ii) estimate second virial coefficients using both approximate theory and computer simulations. In agreement with experiment, a Hofmeister reversal for protein-protein interactions is observed when crossing iso-electric conditions. Thiocyanate binding further leads to large charge fluctuations that may trigger intermolecular charge regulation interactions.
authors.affiliation: Department of Theoretical Chemistry, Lund University, P.O.B. 124, SE-22100 Lund, Sweden. anil.kurut@teokem.lu.se
authors.forename: Anil
authors.initials: A
authors.lastname: Kurut
authors.forename: Mikael
authors.initials: M
authors.lastname: Lund